Induction device and magnetic circuits for the same



EXANHNER.

Aug. 25, 1925.

J. A, DURAN INDUCTION DEVICE- AND MAGNETIC CIRCUITS FOR THE SAME FiledSept. 15 1924 v 2 Sheets-Sheet WHVEINTCJ T A LNIUW QR J W EXAMWER,

Aug. 25, 1925.

.1. A. DORAN INDUCTION DEVICE AND MAGNETIC CIRCUITS FOR THE SAME FiledSept. 15. 1924 2 Sheets-t3heet 2 Patented Au 25, 1925.

UNITED STATES fixer/amen PATENT OFFICE.

JAMES A. DOBAN, OF PROVIDENCE, BIIODE ISLAND.

INDUCTION DEVICE AND MAGNETIC CIRCUITS .FQR- THE SAME.

Application filed septemher 15, 1924.

T all whom it may concern:

Be it known that I, J AMEs A. DoRAN, citizen of the United States, anda. resident of Providence, in the county of Providence and State ofRhode Island, have invented a new and useful Improvement in InductionDevices and Magnetic Circuits for the Same, of which the following is aspecification.

My invention relates to induction devices such as induction coils, sparkcoils, transformers for electric distribution, telephony, radiocommunication, et cetera, solenoids and the like, and to magneticcircuits for the same; and the object of said invention is to provide adevice of the character specified which shall have practically noexternal field, which may be readily ventilated or cooled by oil and themagnetic circuit of which shall have minimum reluctance, and otherwiseto improve and simplify the construction of the same and increase theefiiciency thereof in the manner hereinafter more fully set forth.

In the drawings which accompany and form a part of this specification-Figure 1 is an elevation of a transformer embodying my invention whichis particularly adapted for use in radio receiving systems;

2 is a central longitudinal section of said transformer;

Figs. 3, 4 and 5 are transverse sections taken respectively on the lines8-3, 44, 5-5 of Fig. 2;

Fig. 6 is a transverse section of a modification in which an auxiliaryfield is employed;

Fig. 7 is a transverse section of another modification in which thetransformer windings are separated from each other and from the core toprovide cooling passages;

Fig. 8 is a transverse section of a further modification in which aplurality of primary and secondary windings are employed, each primarybeing spaced apart from its secondary to provide a cooling passage.

Fig. 9 is a fragmentary plan view of the underside of the insulationcap.

In the particular drawings selected for more fully disclosing myinvention 10 represents an axially-laminated core herein shown asconsisting of a number of tubes each provided with a longitudinal slot11. Preferably the core is formed by winding an Serial No. 737,774.

iron ribbon on a mandrel and sawing said slot therethrough. It is to beunderstood however that said core is not necessarily tubular and may beformed. of wire or plates of varying widths.

An axially-laminated field 12, herein shown as tubular and as slottedlongitudinally at 13, encloses the core and is spaced therefrom.

The magnetic circuit is completed by the field caps 14, which arelaminated and slotted radially as shown at 16, 17, said capsmagnetically connecting the ends of the field and core. In the presentinstance the inner faces of each of said field caps are cupped asindicated at 18, 18 for receiving the ends of the core. A casing 19preferably of magnetic material encloses the field and rests on thebase-plate 20, which likewise is of magnetic material. Disposedconcentrically with the core and field are the primary and secondarywindings 21, 22, respectively, the terminals 23, 23 of said windingspass ing through holes 24, 24 which preferably are eyeleted, in theupper field cap 14 and being connected to the bindingpost screws 25, 25which pass through the insulation cap 26.

In order to prevent the turning of said screws and the twisting of thetransformer lead-wires, the heads of said screws are poly angular andthe apertures in the insulation cap through which said screws pass, arecountersunk poly-angularly to receive said heads, as indicated at 26(Fig. 9). The several parts may conveniently be assembled and held inposition by the bolt 27 which passes through the base-plate, the coreand the field caps, a nut 28 being threaded to said bolt toclamp theseveral parts of the magnetic circuit together, and then after thebindingpost screws have been soldered to the lead-wires and insertedthrough the insulation cap 26, the latter is clamped to the easing 19 bythe nut 29 which is threaded to said bolt.

A lock-nut 30 may be employed and affords a convenient means forattaching a conductor for grounding the core as is sometimes desirablewhen the transformer is used as an audio-frequency amplifier in aradioreceiving set.

Preferably the outer tube of the field should be slightly longer thanthe core in order to provide a clearance space for the coil and preventthe crushing of the same when the nut 28 is tightened.

it will be understood that the slots 11, 13, 16 and 17 are notabsolutely essential, but they are desirable for minimizing eddycurrents.

The proportions of the magnetic circuit should be such that thecross-sectional area of the core 10 is substantially equal to thecross-sectional area of the held 12 and to the central cross-sectionalarea of each of the field caps 1st, 15.

The magnetic circuit above described will prevent leakage of magneticflux into the space surrounding the inductance device with which it isused,in other words, the external field is practically nil whichincreases the efficiency of the device and prevents disturbances inadjacent instruments and circuits, a feature which is especiallyimportant in radio apparatus.

Heretofore it has been customary to provide a laminated magnetic circuitconsisting of flat plates of the shape required to complete the circuitaround the coils, and this results in producing a magnetic path in oneplane only. When the primary is energized the resulting flux passesthrough the core and the tendency is to return by a radial path to theopposite end of the core. The reluctance of the iron field being ofcourse very much less than that of the air, a singlcplane core and fieldprovides an unnatural path for the flux with consequent leakage into thespace surrounding the transformer.

It is in part due to this fact that in radiorecciving apparatus only twostages of audio-frequency amplification can with advantage be used, andit is well known that the amplification obtained by audio-frequencytransformers of the prior art varies materially with the frequencies ofthe currents employed. 1 have found, however, that by means of myimproved construction the amplification obtained is much higher over awider frequency band than with tranr; formers having single-plane fieldsand cores, and furthermore that the almost entire absence of externalfield permits the use of four or even more stages of audio-frequencyampli tication without distortion.

l have discovered also that my improved magnetic circuit permits the useof a much higher ratio of transforn'iation than heretofore foundpossible which. augments the work done by each amplification stage.

Another advantage of my improved magnetic circuit is that theamplification obtained by means of the high ratio of transformationaforesaid is effective over a frequency band almost as wide as in thecase of transformers having a much lower transformation ratio.

A further advantage of my construction assesseis the reduced cost of thedevice resulting from the fact that the core of circular crosssectionmay be smaller in diameter than a square core, this resulting in coilsof smaller diameter and less wire for a given effect.

The several parts of the magnetic circuit are clamped tightly together,thus eliminating mechanical vibration which in radio work causesundesirable noises, and is otherwise deleterious.

The fact that the surface of the round core 10 is close against theprimary coil results in higher etiiciency than where flatplatelamination is used and the section of the core is rectangular for suchrectangularsectioned core is commonly employed with a coil having around central hole which results in energy losses.

In Fig. 6 an auxiliary axially-laminated tubular field 31 is interposedbetween the primary 21 and the secondary 22, said field preferably beingslotted longitudinally as indicated at 32. In Fig. 8 the primary andsecondary windings are each made in two sections, 21, 21 being thesections of the primary, and 22, 2:2 those of the secondary, and theauxiliary field 31 is interposed between two of the coils, herein shownas the secondary 22 and the primary 21. In both cases the advantage isobtained that the magnetic flux is kept nearer the center and passesmore uniformly through the secondaries.

In Fig. 7 the primary and secondary coils 21, 22 are spaced from eachother, preferably by the tubes 33, 33 to provide the cooling passage 3 1for ventilation or oil cooling, and the primary is spaced away from thecore by the tube 35 to provide the cooling space 36. Obviously the core10 may have one or more tubes omitted for the same purpose.

Ventilating passages 37, 38 are formed in the arrangement shown in Fig.8 by spacing each primary from its secondary by means of the iron tubes39, 39, 10, 10 which are longitudinally slotted at 41, 12, respectively.The constructions shown in Figs. 6, 7 and 8 are especially applicable tothe distribution of power where iron losses are serious and existconstantly while the primaries are energized. even although there is noload on the secondary.

My improved magnetic circuit results in a. sn'ialler iron loss than theusual fiat-plate circuit, as a much greater surface of iron can beplaced in equivalent space. In large transformers used in electricdistribution flux leakage causes variable voltage, and inasmuch as myimproved magnetic circuit has practically no flux leakage even in largepower or lighting transformers under all conditions of variable load, Iam enabled to eliminate this difliculty.

Having thus described illustrative embodi- IOU ments of my inventionwithout however limiting the same thereto, what I claim and desire tosecure by Letters Patent is:

1. A magnetic circuit for an induction device comprising anaxially-laminated tubular core, an axially-laminated tubular fieldenclosing said core and spaced therefrom, and laminated field capsmagnetically connecting the ends of said core and field.

2. A magnetic circuit for an induction device comprising anaxially-laminated longitudinally-slotted tubular core, anaxiallylaminated tubular field enclosing said core and spaced therefrom,and laminated field caps magnetically connecting the ends of said coreand field.

3. A magnetic circuit for an induction device comprising anaxially-laminated tubular core, an axially-laminatedlongitudinally-slotted tubular field enclosing said core and spacedtherefrom, and laminated filed caps magnetically connecting the ends ofsaid core and field.

4. A magnetic circuit for an induction device comprising anaxially-laminated tubular core, an axially-laminated tubular fieldenclosing said core and spaced therefrom, and laminated radially-slottedfield caps magnetically connecting the ends of said core and field.

5. A magnetic circuit for an induction de vice comprising anaxially-laminated tubular core, an axially-laminated tubular fieldenclosing said core and spaced therefrom, an axially-laminated auxiliarytubular field concentric with and spaced from said core and field, andlaminated field caps magnetically connecting the ends of said core,field and auxiliary field.

6. A magnetic circuit for an induction device comprising anaxially-laminated tubu lar core, an axially-laminated tubular fieldenclosing said core and spaced therefrom, and axially-laminatedlongitudinally-slotted auxiliary tubular field concentric with andspaced from said core and field, and laminated field caps magneticallyconnecting the ends of said core, field and auxiliary field.

7. A transformer comprising an axiallylaminated core, anaxially-laminated field enclosing said core and spaced therefrom,laminated field caps magnetically connecting the ends of said core andfield, and windings disposed concentrically with said core and field,said windings being spaced from each other to provide cooling passages.

8. A transformer comprising an axiallylaminated core, anaxially-laminated field enclosing said core and spaced therefrom,laminated field caps magnetically connecting the ends of said core andfield, and windings disposed concentrically with said core and field,one of said windings being spaced from said core to provide coolingpassages.

9. A transformer comprising an axially- EXAMINER,

laminated core, an axially-laminated field enclosing said core andspaced therefrom, laminated field caps magnetically connecting the ends.of said core and field, a plurality of primary windings disposedconcentrically with said core and field, a plurality of secondarywindings disposed concentrically with said core and field, and anaxially-laminated auxiliary field magnetically connected to said capsand interposed between two of said windings.

10. A transformer comprising an axiallylaminated core, anaxially-laminated field enclosing said core and spaced therefrom,laminated field caps magnetically connecting the ends of said core andfield, and a plurality of pairs of primary and secondary windingsdisposed concentrically with said core and field, each primary windingbeing spaced from its secondary to provide a cooling passage.

11. A magnetic circuit for an induction device comprising anaxially-laminated core, an axially-laminated field enclosing said coreand spaced therefrom, and laminated field caps magnetically connectingthe ends of said core and field, the cross-sectional area of said corebeing substantially equal to the cross-sectional area of said field andto the central cross-sectional area of each of said caps.

12. A magnetic circuit for an induction device comprising anaxially-laminated tubular core, and laminated field caps magneticallyconnected to the ends of said core, the inner faces of each of said capsbeing cupped to receive the ends of said core.

13. A transformer comprising an axiallylaminated core, anaxially-laminated field enclosing said core and spaced therefrom,laminated field caps magnetically connecting the ends of said core andfield, said core and caps each being provided with a central bore, abase-plate disposed on one of said caps, a bolt passing through saidbaseplate, core and caps, a. nut threaded to the end of said bolt forbinding the several parts to gether, acasing having one end resting onsaid base-plate and concentric with said field, an insulation capresting on the other end of said casing, said cap being provided with acentral bore for receiving said bolt, a nut threaded to the end of saidbolt projecting through said insulation cap for binding said cap to saidcasing, windings disposed concentrically with said field and core, theterminals of said windings passing through apertures in the field capadjacent to said insulation cap, and bindingposts passing through saidinsulation cap, the terminals of said windings being connectedrespectively to said bindingposts.

14. A transformer comprising a core, primary and secondary windingsdisposed concentrically with said core, a casing enclosing saidwindings, and bindingposts secured to the ends of said screws projectingbeyond 10 said insulation cap.

In testimony whereof, I have hereunto subscribed my name this 12th dayof Septeinber, 1924;.

JAMES A. DOE-AN.

